Human circulatory system can be differentiated into two sub-systems. These are arterial system and venous system. The first system is arterial system left ventricle pumps oxygenated blood into aorta with full force. In aorta the speed of blood is very high.

The first arteries branching off from the aorta are coronary arteries. These arteries supply the oxygenated blood and food to heart itself. Aorta then forms an arch and before descending down gives off three branches one on each side. Common carotid arteries supplying blood to head region, innominate artery to upper parts of the limbs and sub Clavien artery to arms.

Aorta descends down along with vertebral column.It then gives off Coeliac artery which supplies blood to stomach and spleen, Mesenteric arteries to parts of digestive systems like duodenum, pancreases, intestine and rectum. Hepatic artery supplies the blood to liver and pair of renal arteries to kidneys. The aorta then bifurcates to form right and left iliac arteries which supply the blood to right and left legs.

 Pulmonary artery originates from right ventricle and carries deoxygenated blood to lungs. The second system is venous system. The deoxygenated blood then poured into right auricle through two major veins. The first is superior vena cava and second is inferior vena cava. Superior vena cava is formed by the union of many veins which brings blood from head, neck, shoulder and arm.

Right and left veins brings the oxygenated blood upwards from the legs and join together to make a large vein. In the way back to the heart, this veins receives blood from iliac veins, hepatic vein which brings blood from liver and right and left renal veins which bring blood from kidney and joined joins main trunk .this vein ,inters the right arteries the heart as inferior Vena Caca.Pulmaonary veins orginate from lungs and bring oxygenates blood to left artrium.